When Gil Kerlikowske took office as drug czar four years ago, he said he was going to retire the concept of the war on drugs. During Obama’s first term, however, his policies did not live up to the bold rhetoric. There were a handful of reforms -- perhaps most notably, a reduction (though not elimination) of the disparity between crack and powder cocaine. But at its core, federal drug policy remained almost entirely unchanged between 2009 and 2012.

In recent weeks, the Obama administration has turned its words into action by tackling one of the most significant and criticized features of the drug war: mandatory minimum sentencing.

Enacted in the 1980s, the mandatory minimum drug sentencing laws were the embodiment of the “war on drugs” mentality. Indeed, it’s difficult to think of another federal law or policy as closely linked to the drug war.

Last month, Attorney General Eric Holder announced a new charging policy, instructing federal prosecutors not to seek mandatory minimum sentences in drug cases that met certain criteria. With some of the criteria left open to interpretation, I wrote last month that only time would tell the policy’s true impact. Will the Department of Justice closely monitor local prosecutors to ensure compliance and consistent interpretation of the policy? Or, will federal prosecutors be given the leeway to circumvent or narrowly apply the new policy?

While it will take at least a few more months to know the answers to these questions, last week Attorney General Holder issued a second memo that provides reason for optimism. Holder’s most recent memo expands the new policy by applying it to defendants who have already been charged and encouraging prosecutors to follow the guidance even in cases where the defendant has already pled guilty and is awaiting sentencing, where it is “legally and practically feasible.”

This development is a hopeful sign that the Department of Justice is serious about its new policy.

Of course, the executive branch can do only so much on its own. It will take an act of Congress to change the mandatory minimum laws for good. And, even without mandatory minimums, federal drug defendants still face needlessly lengthy prison terms under the advisory Sentencing Guidelines.

Ending the drug war won’t be as simple as reforming any one law or policy, even one as important as mandatory minimum sentencing. The drug war was built over decades and involves many moving parts.

But if the Obama administration really does want to start the process of dismantling the war on drugs, there’s no better place to start than with mandatory minimums.